1. Field of the Invention
This invention is directed to a process and system for improving the efficiency of internal combustion engines and thereby lowering the resultant emissions while improving fuel economy. More specifically, this invention relates to a process whereby a small percentage of the fuel employed is vaporized and sent to the cylinder or combustion chamber of the engine.
2. Description of the Prior Art
It has long been known that internal combustion engines in general, and gasoline engines of all types, diesel and jet engines in particular are not 100% efficient, i.e., the total theoretical energy yield from the fuel consumed is not realized by the engine in operation. This inefficiency not only results in a severe cost, in terms of fuel consumed, for the use of the engine, but results in substantially higher emissions of pollutants such as NO.sub.x gases, hydrocarbons, and CO that is neither safe or desirable.
Accordingly, there have been repeated attempts to improve the efficiency of internal combustion engines. One particular practice that has received a great deal of attention is the replacement of a carburetor in a gasoline engine with a fuel vaporizing or fuel/air mixing device that takes over the carburetor mixing function. However, such systems are prohibitively expensive, if not physically impractical, to install in existing engines and would require extensive and expensive retooling of engine production lines in order to employ them.
An alternative that has also been proposed to improve combustion efficiency is the evaporation apparatus of U.S. Pat. No. 4,159,698. That apparatus, limited to gasoline engines and not suitable for use in non-carburetor engines, diesel engines, jet engines, etc. involves the evaporation of a portion of the fuel which is directed to the combustion cylinder through apparatus downstream of the carburetor. Although the evaporation apparatus process of this reference may reduce certain pollutants, it does not have wide applicability to any type of engine, and it is also unsuitable for improving fuel efficiency in a fuel demand situation as the evaporation apparatus cannot be adequately controlled to provide the necessary fuel vapor.
Another problem, perhaps the most serious of those encountered, is the belief that, due to their operation on different principles, a method for improving combustion efficiency in one engine would not be suitable for use in another engine. In particular, devices such as the evaporation system discussed above provide a "pre-charge" of vaporized fuel into the cylinder in which combustion takes place. Although possibly suitable for gasoline engines, it has widely been held that such preinjection would not be suitable for diesel engines, due to the problems of preignition. Diesel engines differ from gasoline engines in that air drawn into the cylinders is compressed and thus heated above autoignition temperature of the injected diesel fuel charge. In gasoline engines, gasoline and air vapor is ignited by a sparkplug and is at all times below autoignition temperatures.
When fuel/air mixtures are autoignited too early, preignition or knocking occurs, resulting in damage to the engine. Preignition or knocking can occur in diesel engines by injecting fuel through the injectors too early in the engine combustion cycle; that is, too far before the piston reaches "top-dead-center".
Accordingly, it has been widely held that fuel vapor in the intake air would cause preignition. Thus, systems designed for gasoline engines which provide fuel vapors in an air stream have not been employed, and in fact, have been deliberately avoided, in connection with diesel engines.
It is of course true that both rotary engines and jet engines provide even greater differences which must be overcome in the provision of a universally acceptable fuel vapor air intake system.
Accordingly, there continues to be a widespread need in the art for development of a system which improves the efficiency of internal combustion engines which is universally acceptable and can be retrofitted to existing engines as well as installed in new engines, without substantial expense and retooling.